SSQ1 encodes a specialized mitochondrial Hsp70-type chaperone dedicated to iron-sulfur (Fe/S) cluster biogenesis. Ssq1p mediates the ATP-dependent transfer of newly assembled Fe/S clusters from the scaffold proteins Isu1/Isu2 to the downstream carrier Grx5, working together with its J-protein co-chaperone Jac1 and the nucleotide exchange factor Mge1. This transfer step is essential for maturation of all cellular Fe/S proteins, both mitochondrial and cytosolic. Ssq1p is also involved in maturation of the frataxin homolog Yfh1, which itself participates in Fe/S cluster assembly as an iron donor. Unlike the general-purpose mitochondrial Hsp70 Ssc1, Ssq1p has evolved a highly specific interaction with the conserved LPPVK motif of Isu1/Isu2, reflecting its dedicated role in Fe/S cluster transfer rather than general protein folding.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005737
cytoplasm
|
IBA
GO_REF:0000033 |
KEEP AS NON CORE |
Summary: Manual review: cytoplasm may be context-dependent or peripheral for SSQ1.
Reason: Kept as non-core to preserve potentially valid context-specific annotation without elevating it to core function.
|
|
GO:0005739
mitochondrion
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: mitochondrion is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0016887
ATP hydrolysis activity
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0031072
heat shock protein binding
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: heat shock protein binding is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0044183
protein folding chaperone
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: protein folding chaperone is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0016226
iron-sulfur cluster assembly
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0042026
protein refolding
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Manual review: protein refolding is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0000166
nucleotide binding
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Manual review: nucleotide binding is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005524
ATP binding
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Manual review: ATP binding is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005739
mitochondrion
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: Manual review: mitochondrion is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005759
mitochondrial matrix
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: Manual review: mitochondrial matrix is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0016787
hydrolase activity
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Manual review: hydrolase activity is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0016887
ATP hydrolysis activity
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0070013
intracellular organelle lumen
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: Manual review: intracellular organelle lumen is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005515
protein binding
|
IPI
PMID:12756240 Ssq1, a mitochondrial Hsp70 involved in iron-sulfur (Fe/S) c... |
MARK AS OVER ANNOTATED |
Summary: Manual review: protein binding is too generic or over-extended for SSQ1.
Reason: Marked over-annotated because more specific terms capture the biology more accurately.
|
|
GO:0005515
protein binding
|
IPI
PMID:12947415 An interaction between frataxin and Isu1/Nfs1 that is crucia... |
MARK AS OVER ANNOTATED |
Summary: Manual review: protein binding is too generic or over-extended for SSQ1.
Reason: Marked over-annotated because more specific terms capture the biology more accurately.
|
|
GO:0005515
protein binding
|
IPI
PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... |
MARK AS OVER ANNOTATED |
Summary: Manual review: protein binding is too generic or over-extended for SSQ1.
Reason: Marked over-annotated because more specific terms capture the biology more accurately.
|
|
GO:0005515
protein binding
|
IPI
PMID:19536198 An atlas of chaperone-protein interactions in Saccharomyces ... |
MARK AS OVER ANNOTATED |
Summary: Manual review: protein binding is too generic or over-extended for SSQ1.
Reason: Marked over-annotated because more specific terms capture the biology more accurately.
|
|
GO:0005515
protein binding
|
IPI
PMID:37968396 The social and structural architecture of the yeast protein ... |
MARK AS OVER ANNOTATED |
Summary: Manual review: protein binding is too generic or over-extended for SSQ1.
Reason: Marked over-annotated because more specific terms capture the biology more accurately.
|
|
GO:0016226
iron-sulfur cluster assembly
|
IMP
PMID:11171977 Jac1, a mitochondrial J-type chaperone, is involved in the b... |
ACCEPT |
Summary: Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0044571
[2Fe-2S] cluster assembly
|
IMP
PMID:11273703 The mitochondrial proteins Ssq1 and Jac1 are required for th... |
ACCEPT |
Summary: Manual review: [2Fe-2S] cluster assembly is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005739
mitochondrion
|
IMP
PMID:11273703 The mitochondrial proteins Ssq1 and Jac1 are required for th... |
ACCEPT |
Summary: Manual review: mitochondrion is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0006879
intracellular iron ion homeostasis
|
IMP
PMID:9660806 Mt-Hsp70 homolog, Ssc2p, required for maturation of yeast fr... |
KEEP AS NON CORE |
Summary: Manual review: intracellular iron ion homeostasis may be context-dependent or peripheral for SSQ1.
Reason: Kept as non-core to preserve potentially valid context-specific annotation without elevating it to core function.
|
|
GO:0016887
ATP hydrolysis activity
|
IDA
PMID:12756240 Ssq1, a mitochondrial Hsp70 involved in iron-sulfur (Fe/S) c... |
ACCEPT |
Summary: Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0051082
unfolded protein binding
|
IDA
PMID:11601843 The two mitochondrial heat shock proteins 70, Ssc1 and Ssq1,... |
MODIFY |
Summary: Manual review: unfolded protein binding is better represented by a more specific replacement term for SSQ1.
Reason: Modified to align with current curation guidance and improve term specificity.
Proposed replacements:
protein folding chaperone
|
|
GO:0005739
mitochondrion
|
HDA
PMID:24769239 Quantitative variations of the mitochondrial proteome and ph... |
ACCEPT |
Summary: Manual review: mitochondrion is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005739
mitochondrion
|
HDA
PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... |
ACCEPT |
Summary: Manual review: mitochondrion is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0005759
mitochondrial matrix
|
IDA
PMID:8707841 The cold sensitivity of a mutant of Saccharomyces cerevisiae... |
ACCEPT |
Summary: Manual review: mitochondrial matrix is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
|
GO:0016226
iron-sulfur cluster assembly
|
IMP
PMID:9813017 Suppressors of superoxide dismutase (SOD1) deficiency in Sac... |
ACCEPT |
Summary: Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.
Reason: Retained as supported or plausible for this gene and evidence context.
|
id: Q05931
gene_symbol: SSQ1
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:559292
label: Saccharomyces cerevisiae
description: >-
SSQ1 encodes a specialized mitochondrial Hsp70-type chaperone dedicated to
iron-sulfur (Fe/S) cluster biogenesis. Ssq1p mediates the ATP-dependent
transfer of newly assembled Fe/S clusters from the scaffold proteins
Isu1/Isu2 to the downstream carrier Grx5, working together with its
J-protein co-chaperone Jac1 and the nucleotide exchange factor Mge1. This
transfer step is essential for maturation of all cellular Fe/S proteins,
both mitochondrial and cytosolic. Ssq1p is also involved in maturation of
the frataxin homolog Yfh1, which itself participates in Fe/S cluster
assembly as an iron donor. Unlike the general-purpose mitochondrial Hsp70
Ssc1, Ssq1p has evolved a highly specific interaction with the conserved
LPPVK motif of Isu1/Isu2, reflecting its dedicated role in Fe/S cluster
transfer rather than general protein folding.
existing_annotations:
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: cytoplasm may be context-dependent or peripheral for SSQ1.'
action: KEEP_AS_NON_CORE
reason: Kept as non-core to preserve potentially valid context-specific annotation without elevating it to core function.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: mitochondrion is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0016887
label: ATP hydrolysis activity
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0031072
label: heat shock protein binding
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: heat shock protein binding is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0044183
label: protein folding chaperone
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: protein folding chaperone is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0016226
label: iron-sulfur cluster assembly
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0042026
label: protein refolding
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'Manual review: protein refolding is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0000166
label: nucleotide binding
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'Manual review: nucleotide binding is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005524
label: ATP binding
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: 'Manual review: ATP binding is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: 'Manual review: mitochondrion is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: 'Manual review: mitochondrial matrix is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0016787
label: hydrolase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'Manual review: hydrolase activity is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0016887
label: ATP hydrolysis activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: 'Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0070013
label: intracellular organelle lumen
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: 'Manual review: intracellular organelle lumen is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:12756240
review:
summary: 'Manual review: protein binding is too generic or over-extended for SSQ1.'
action: MARK_AS_OVER_ANNOTATED
reason: Marked over-annotated because more specific terms capture the biology more accurately.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:12947415
review:
summary: 'Manual review: protein binding is too generic or over-extended for SSQ1.'
action: MARK_AS_OVER_ANNOTATED
reason: Marked over-annotated because more specific terms capture the biology more accurately.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:16554755
review:
summary: 'Manual review: protein binding is too generic or over-extended for SSQ1.'
action: MARK_AS_OVER_ANNOTATED
reason: Marked over-annotated because more specific terms capture the biology more accurately.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:19536198
review:
summary: 'Manual review: protein binding is too generic or over-extended for SSQ1.'
action: MARK_AS_OVER_ANNOTATED
reason: Marked over-annotated because more specific terms capture the biology more accurately.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:37968396
review:
summary: 'Manual review: protein binding is too generic or over-extended for SSQ1.'
action: MARK_AS_OVER_ANNOTATED
reason: Marked over-annotated because more specific terms capture the biology more accurately.
- term:
id: GO:0016226
label: iron-sulfur cluster assembly
evidence_type: IMP
original_reference_id: PMID:11171977
review:
summary: 'Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0044571
label: '[2Fe-2S] cluster assembly'
evidence_type: IMP
original_reference_id: PMID:11273703
review:
summary: 'Manual review: [2Fe-2S] cluster assembly is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IMP
original_reference_id: PMID:11273703
review:
summary: 'Manual review: mitochondrion is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0006879
label: intracellular iron ion homeostasis
evidence_type: IMP
original_reference_id: PMID:9660806
review:
summary: 'Manual review: intracellular iron ion homeostasis may be context-dependent or peripheral for SSQ1.'
action: KEEP_AS_NON_CORE
reason: Kept as non-core to preserve potentially valid context-specific annotation without elevating it to core function.
- term:
id: GO:0016887
label: ATP hydrolysis activity
evidence_type: IDA
original_reference_id: PMID:12756240
review:
summary: 'Manual review: ATP hydrolysis activity is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0051082
label: unfolded protein binding
evidence_type: IDA
original_reference_id: PMID:11601843
review:
summary: 'Manual review: unfolded protein binding is better represented by a more specific replacement term for SSQ1.'
action: MODIFY
reason: Modified to align with current curation guidance and improve term specificity.
proposed_replacement_terms:
- id: GO:0044183
label: protein folding chaperone
- term:
id: GO:0005739
label: mitochondrion
evidence_type: HDA
original_reference_id: PMID:24769239
review:
summary: 'Manual review: mitochondrion is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: HDA
original_reference_id: PMID:16823961
review:
summary: 'Manual review: mitochondrion is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: IDA
original_reference_id: PMID:8707841
review:
summary: 'Manual review: mitochondrial matrix is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
- term:
id: GO:0016226
label: iron-sulfur cluster assembly
evidence_type: IMP
original_reference_id: PMID:9813017
review:
summary: 'Manual review: iron-sulfur cluster assembly is consistent with known biology of SSQ1.'
action: ACCEPT
reason: Retained as supported or plausible for this gene and evidence context.
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: PMID:11171977
title: Jac1, a mitochondrial J-type chaperone, is involved in the biogenesis of Fe/S clusters in Saccharomyces cerevisiae.
findings: []
- id: PMID:11273703
title: The mitochondrial proteins Ssq1 and Jac1 are required for the assembly of iron sulfur clusters in mitochondria.
findings: []
- id: PMID:11601843
title: The two mitochondrial heat shock proteins 70, Ssc1 and Ssq1, compete for the cochaperone Mge1.
findings: []
- id: PMID:12756240
title: Ssq1, a mitochondrial Hsp70 involved in iron-sulfur (Fe/S) center biogenesis. Similarities to and differences from its bacterial counterpart.
findings: []
- id: PMID:12947415
title: An interaction between frataxin and Isu1/Nfs1 that is crucial for Fe/S cluster synthesis on Isu1.
findings: []
- id: PMID:16554755
title: Global landscape of protein complexes in the yeast Saccharomyces cerevisiae.
findings: []
- id: PMID:16823961
title: 'Toward the complete yeast mitochondrial proteome: multidimensional separation techniques for mitochondrial proteomics.'
findings: []
- id: PMID:19536198
title: 'An atlas of chaperone-protein interactions in Saccharomyces cerevisiae: implications to protein folding pathways in the cell.'
findings: []
- id: PMID:24769239
title: Quantitative variations of the mitochondrial proteome and phosphoproteome during fermentative and respiratory growth in Saccharomyces cerevisiae.
findings: []
- id: PMID:37968396
title: The social and structural architecture of the yeast protein interactome.
findings: []
- id: PMID:8707841
title: The cold sensitivity of a mutant of Saccharomyces cerevisiae lacking a mitochondrial heat shock protein 70 is suppressed by loss of mitochondrial DNA.
findings: []
- id: PMID:9660806
title: Mt-Hsp70 homolog, Ssc2p, required for maturation of yeast frataxin and mitochondrial iron homeostasis.
findings: []
- id: PMID:9813017
title: Suppressors of superoxide dismutase (SOD1) deficiency in Saccharomyces cerevisiae. Identification of proteins predicted to mediate iron-sulfur cluster assembly.
findings: []